With accent marks:
Кто о чём, а вши́вый о ба́не.
Who is talking about what, and a lousy one about the bath.
This saying describes a situation when in a conversation of several people, one of them always talks only about what worries him. Even if the discussion is about a completely different thing. In the saying, such a person is compared to a "lousy one talking about the bath". Because until he bathes, and until this does not ease his suffering from the lice biting him, he will not care about anything else.
You can use this saying when someone always falls back on talking about the same thing.
Other Russian proverbs
Time for business, an hour for fun.
Make a fool pray to God - he will break his forehead.
Better to see once than hear a hundred times.
The forbidden fruit is sweet.
Fear has big eyes.
Your own shirt is closer to your body.
Measure seven times, cut one.
A fisherman sees a fisherman from afar.